1. Field of the Invention
The present invention relates to a surface-mounted electromagnetic sound generating body incorporated in mobile communications devices, such as cellular telephones and pagers, that generates an incoming call indicator tone when the device receives an incoming call, and more particularly to a thin surface-mount type electromagnetic sound generating body mounted on the surface of a printed circuit board in a mobile communications device.
2. Description of the Prior Art
A known example of the surface-mounted electromagnetic sound generating body 1 of this kind includes a thin type which incorporates a vibration sound generating unit (not shown) in a rectangular parallelepiped resin casing 2, as shown in FIG. 1. The surface-mounted electromagnetic sound generating body 1, as shown in FIG. 2, is incorporated in a body case 3 such as a mobile phone and mounted on a printed circuit board 4. The casing 2 has a sound release hole 5 formed in one side. When it is surface-mounted on the printed circuit board 4, the body 1 is so arranged that the sound release hole 5 faces an opening 6 formed in the body case 3. When a mobile phone is assembled, a sound leakage prevention packing 7 is provided in a gap between the sound release hole 5 and the opening 6 in the body case 3 to prevent an incoming call indicator tone from becoming indistinct. This packing 7 has a hollow portion 7a, in which the casing 2 of the surface-mounted electromagnetic sound generating body 1 is installed, and a through-hole 7b that communicates the sound release hole 5 with the opening 6. The electromagnetic sound generating body 1 is mounted on the printed circuit board 4 and then the casing 2 is fitted over the body 1 from above. The inner side of the body case 3 around the opening 6 is bonded with a dust prevention cloth 8 to prevent dust, foreign matters, water droplets and humid air from entering into the body case 3. The front side of the packing 7 is pressed against the dust prevention cloth 8. In this state the body 1 is incorporated in the body case 3.
FIG. 3 and 4 show another example of the conventional packing 9, The packing 9 has a hollow portion 9a to cover the front half of the casing 2 and a through-hole 9b for communicating the sound release hole 5 to the opening 6. The packing 9 also has a double-sided adhesive tape 10 attached to the side of the hollow portion 9a around the through-hole 9b. When a mobile phone is assembled, a cover sheet is removed from the double-sided adhesive tape 10, which is then bonded to the periphery of the sound release hole 5 to fix the packing 9 to the casing 2.
With the conventional surface-mounted electromagnetic sound generating body 1 described above in the first and second examples, however, because the body 1 and the packing 7 or 9 are supplied separately to the mobile phone assembly line, the packing 7 or 9 must be attached, in a separate process, to the casing 2 of the body 1 surface-mounted on the printed circuit board 4.
Further, because the packing 7, 9 is formed as a cover that encloses the entire or front half of the casing 2, the volume occupied by the surface-mounted electromagnetic sound generating body 1 on the printed circuit board 4 increases, giving rise to a problem of greater limitations in mounting other parts.